Six-gears Automatic Transmission (bus)

Function

The economic pressure leads to an extremely compact construction which not onlycontains six gears, a torque converter with lock-up clutch, but also a retarder. For heavy utility vehicles the automatic gearbox would be probably a little bit too weak, but for town and long-distance busses approx. 1100 nm of possible input torque are probably sufficient.

How it works

We start on the left of the engine, thus going - as it commonly is with modern low floor busses - from the rear to the front. First there is the torque converter with multi-disc lock-up clutch-wheel, turbine wheel and impeller. It seems that one can even see the freewheel of the guide wheel. Next in the casing are the pump and retarder which are connected by largely dimensioned oil lines to the (front mounted) horizontal oil cooler. In the multiple-disc clutches (green) the hydraulically operated ring pistons (blue) are recognizable. Inside the other multi-disc brakes/-clutches follow three planetary systems, whereby the first two may well be combined. From there it goes out to the short drive shaft and from the rear to the final drive. 09/08